Has the Holder Justice Department corrupted the procedure for investigating public corruption?

As Scott discusses below, the Holder Justice Department reportedly has decided to end its investigation of a pay-to-play regime in New Mexico involving one of Governor Bill Richardson’s largest political donors. It was this investigation that cost Richardson the Secretary of Commerce post.
According to AP, the investigation “was killed in Washington” by top DOJ officials. Faithful readers know that I have no problem with top DOJ officials killing investigations as long as they don’t do so for improper reasons, such as a connection between a potential target (here Richardson) and the president (here Obama).
However, Hans von Spakovsky, a former DOJ official himself, points out that the Department has a manual called “Federal Prosecution of Election Offenses” that sets out the rules and procedures for U.S. attorneys when they are investigating these types of public-corruption cases. According to von Spakovsky, under these rules and procedures it is the U.S. attorney in New Mexico who would normally make the final call on a local public-corruption case, not “top Justice Department officials” in Washington. The U.S. attorney is required to “consult” with the Public Integrity Section of the Criminal Division in Washington, but the final decision rests with the U.S. attorney.
Accordingly, if the AP is correct that “top” officials in Washington killed the investigation, then political appointees within the department did not follow normal DOJ procedures.
If this were happening under a Republican administration, the usual suspects — Democratic Senators, the Washington Post, etc. — would be oozing outrage, and calls for an investigation would already be heard. But since this is happening under a Democratic administration, the usual suspects are silent.